The present invention relates to a method for the preparation of acyl cyanides. More particularly, the present invention relates to a method for the preparation of acyl cyanides which does not require the use of a copper salt catalyst.
Acyl cyanides are important intermediate products from which other important products, such as herbicides and photoinitiators, can be prepared. The heretofore available methods for their preparation have been limited in number and are generally characterized by the use of HCN or NaCN with a copper (I) salt as catalyst.
Thus, for example, it is well-known in the art to prepare benzoyl cyanide by reacting over-stoichiometric amounts of cuprous cyanide with benzoyl chloride at temperatures up to about 80.degree. C. in acetonitrile or n-butyronitrile; or at temperatures ranging from about 220.degree. C. to about 230.degree. C. in the absence of a solvent.
U.S. Pat. No. 4,113,773 discloses a method for the preparation of benzoyl cyanide wherein a reaction mixture is formed of benzoyl chloride, an alkali cyanide, a carboxylic acid nitrile and a copper (I) salt; and is reacted at a temperature ranging from about 50.degree. C. to about 160.degree. C.
German Offenlegungsschrift No. 2,614,242 discloses a method for preparing acyl cyanides wherein an acyl halide is reacted with an alkali cyanide or hydrocyanic acid in the presence of a heavy metallic cyanide as catalyst.
The heavy metallic cyanide generally used is cuprous cyanide, although zinc cyanide is also mentioned.
The cuprous cyanide employed in these prior art methods is difficult to obtain and often is air oxidized, on storage, to the relatively inactive copper (II) state.
Therefore, a need exists for a new method for the preparation of acyl cyanides in which the catalyst employed is readily available and retains its activity during storage.
It is an object of the present invention to provide a method for the preparation of acyl cyanides wherein the material used as catalyst is readily available and stable.